The present invention relates to a hybrid car control apparatus wherein either the front wheels or the rear wheels of the car are driven by the engine and the other wheels are driven by a motor.
The present invention relates to a simplified hybrid car control apparatus wherein a car drive motor is directly driven using the electric power produced by a generator driven by an engine, without using the element that absorbs the electric power of a battery or a capacitor.
In a conventional hybrid car, when a wheel driven by the engine has slipped, the slip of the engine driven wheel is reduced by increasing the amount of the electric power produced by a generator connected to the engine, according to known method, for example, as disclosed in Japanese Application Patent Laid-open Publication No. 2001-63392 (see, paragraphs 21 and 22, and FIG. 4). However, this technique fails to give serious consideration to a simplified hybrid car system wherein a car drive motor is directly driven using the electric power produced by the generator driven by the engine, without using the element that absorbs the electric power of a battery or a capacitor.
This known configuration also increases the motor drive current if the amount of electric power produced by the generator is increased to reduce slip at an engine driven wheel, with the result that the motor torque is increased and wheel spin may occur at the motor driven wheel.
In accordance with the present invention, according to the result of various experiments carried out by the inventors of the present invention, what is meant by wheel spin in this connection is defined as a phenomenon in which the slip rate to be defined later (Equation. 2) is reduced below −0.25 when the peripheral speed of the wheel is greater than the car speed.
When wheel spin has occurred, there is a reduction in traction, i.e. a reduction in the torque transferred to the road surface by the wheel, with the result that the acceleration performance deteriorates. If the wheel spin of an engine driven wheel has disappeared, while a motor driven wheel is still subjected to wheel spin, there may be a lack of stability, for example, due to the spinning of the car. This phenomenon tends to occur especially in a car using a simplified hybrid car system where the engine drives the front wheel and the rear wheels are driven by an electric motor.
Further, when both a front wheel and a rear wheel are subjected to wheel spin, it becomes difficult to detect the car body speed, and an adverse effect will be given to other car operation control systems, such as the ABS. To detect the car speed in this case, a new sensor, such as an acceleration sensor, must be added, and this leads to a complicated system configuration and increased costs.